1. Field of the Invention
The present invention relates to a marking for an item or article. The marking comprises a chiral liquid crystal polymer (CLCP) in the form of randomly distributed CLCP particles such as, e.g., flakes or in the form of a CLCP layer having randomly distributed craters therein. The detectability of the particles or craters is improved by including a particular luminescent substance in the marking and/or the substrate covered by the marking
2. Discussion of Background Information
Every minute billions of items, services and goods are exchanged between people around the world. Some are immaterial and some are tangible, such as, e.g., pharmaceuticals, luxury goods, cigarettes, wine, olive oil, food or banknotes, used for different purposes such as to cure a disease, to provide pleasant moments, to protect us, to pay for something or simply for eating. Although the majority of said items, services and goods is genuine, there is a small part of them that is fake or counterfeit and even worse, may be toxic, especially in the pharmaceutical field or in the case of alcoholic goods. There is not a single day where there will not be a newspaper article somewhere around the world that reports of corresponding problems. This is becoming an increasingly critical problem for all nations and affects not only the economy (at issue are about hundred billions of diversion and counterfeit products) but unfortunately also affects the health of human beings.
For decades attempts to solve this problem have successfully been made, but unfortunately always only for a limited period of time because counterfeiters which now are also linked to criminal organisations develop and improve their skills in parallel with the evolution of the technology and are able to offer to customers fake or non-genuine products which cannot be distinguished from the genuine products by mere visual inspection. This forces the providers of security solutions to constantly be not only up to date, but to be ahead of the counterfeiters in terms of new security features.
In the early days of the development of security features the simple addition of fluorescent compounds to a specific ink was sufficient and may even today still be sufficient as a first level of protection against counterfeit or fake products. But as is often the case, new fake products with markings which mimic the genuine ones have emerged and make it necessary to develop ever more sophisticated and complex inks to overcome this problem.
Another type of security features which has been in use for the last twenty years or so is based upon the random distribution of particles inside a medium. These security features not only deter the selling of counterfeit products because they are difficult to forge, but also provide the ability to create a unique identifier for the items or goods that comprise these security features. The randomly distributed particles may, for example, be CLCP flakes or the like. However, if the CLCP flakes are to be detected by irradiating the security feature and measuring the radiation reflected by the flakes there is the problem that the detectability of radiation reflected by a particular flake by the device that is to capture the reflected radiation depends on the orientation of the flake inside the marking, i.e., its orientation relative to the position of the device. For example, a flake which is oriented parallel to the direction of radiation cannot be detected because in this case there is no incident radiation and thus, no radiation that can be reflected by the flake. It would therefore be advantageous to have available a security feature that comprises randomly distributed CLCP flakes which can be detected by measuring the radiation reflected by the flakes, independently of the orientation of the flakes relative to the position of the source of radiation employed.
A further recently proposed type of security features comprises a CLCP layer which has randomly distributed craters (holes) therein (see International Patent Application PCT/EP2012/076507). The distribution of the craters is a characteristic of the security feature that can be used to verify the authenticity of an item or article provided carrying the security feature by collecting information relating to the radiation that is reflected by the CLCP material and comparing it with corresponding stored information. However, depending on the nature of the substrate on which the CLCP layer with craters is present, the contrast between the CLCP layer and the areas where no CLCP material is present (i.e., the craters) may not be very strong, rendering the detection of (all of) the craters that are present in the CLCP layer difficult and sometimes impossible. It would thus, be advantageous to be able to increase the contrast between the craters and the CLCP material surrounding them and thus, increase the detectability of the craters.
It has surprisingly been found that the drawbacks of the prior art can be overcome by using together with the CLCP material a luminescent substance whose range of luminescence wavelengths at least partially overlaps the range of reflection wavelengths of the CLCP material.